1. Field of the Invention
The present invention concerns a method for bending an initially flat gypsum board into a durably retained curvilinear shape, and further relates to equipment which may be used at a construction site to produce such bending.
2. Description of the Prior Art
Flat panels, often referred to as “drywalls” or “gypsum boards” are commonly employed in the fabrication of walls and ceilings of interior rooms of buildings. Gypsum board is a laminate structure comprising a core of gypsum sandwiched between a sheet of face paper on one side and a sheet of back paper on the opposite side. Gypsum board is manufactured by a relatively high speed continuous method wherein a slurry of calcined gypsum and various additives is mixed with more than sufficient water for hydration and setting of the gypsum. The slurry is deposited on a lower, continuously advancing paper sheet, and an upper continuously advancing paper sheet is layered over the slurry. The laminate structure is then formed into a continuous flat sheet of paper-enclosed gypsum.
In the typical process the gypsum board is made face side down. The face paper, on the bottom, is folded upward along the two longitudinal edges and folded over onto the top of the slurry along these edges. The back paper is placed-on top of the slurry, overlapping the edge portion of the face paper that is folded over onto the back side of the board. The continuous sheet is carried on a conveyor belt and rollers for a considerable distance until the gypsum core has set to a sufficient degree to permit the board to be cut into normal board lengths and transferred to high temperature drying kilns.
U.S. Pat. No. 5,198,052 to Ali discloses a method for producing a gypsum board having a decoratively shaped surface by applying embossing pressure to the board during its production and before the drying stage. However, Ali does not disclose or contemplate bending of the gypsum board.
Typical interior building construction comprises a plurality of spaced framing members referred to as studs, furring or joists. One or more layers of gypsum board of 3/81″ to ½″ thickness are secured to one or each side of the framing members forming the wall or ceiling surfaces. The side edges of the gypsum boards are generally butted together over a framing member and nailed or screwed thereto with the fasteners extending through the gypsum board and into the framing members. To construct a monolithic appearing wall, the butt joints between adjacent gypsum boards are concealed by covering the joint with a reinforcing joint tape and several layers of a joint compound to cover the joint, the joint tape and the fasteners. To construct a smooth surface without ridges formed by the joint tape and compound, the gypsum board is produced with a slight taper on the face surface adjacent the longitudinal or side edges of the board. The taper results in a slight depression in the wall or ceiling surface at the joints. The depression is filled with the joint compound producing a smooth finish at the joint without a raised ridge.
In certain features of architectural design, it is sometimes desirable to be able to have curved wall panels. Also, vaulted ceilings are often sought but generally avoided because of the expense of traditional construction techniques. Curved gypsum boards, if manufacturable at a factory, would be difficult to transport damage-free to a construction site.
It is accordingly an object of the present invention to produce curved gypsum boards.
It is a further object to produce the aforesaid curved gypsum boards by a low cost process operable at a construction site.
These objects and other objects and advantages of the invention will be apparent from the following description.